AddJsonKeyPropertiesFromSymbol
![AddJsonKeyPropertiesFromSymbol 1:](Images/jpg/13478372875__Web.jpg)
With the aid of this method, metadata can be added via PLC attributes to the JSON representation of a PLC data structure on an FB_JsonSaxWriter object. The method receives as its input parameters the instance of the FB_JsonSaxWriter function block, the desired name of the JSON property that is to contain the metadata, the data type name of the structure and a string variable sProperties, which contains a list of the PLC attributes to be extracted, separated by a cross bar.
Syntax
METHOD AddJsonValueFromSymbol : BOOL
VAR_IN_OUT
fbWriter : FB_JsonSaxWriter;
END_VAR
VAR_IN_OUT CONSTANT
sKey : STRING;
sDatatype : STRING;
sProperties : STRING;
END_VAR
VAR_OUTPUT
hrErrorCode : HRESULT;
END_VAR
Return value
Name | Type |
---|---|
AddJsonValueFromSymbol | BOOL |
/
Inputs/Outputs
Name | Type |
---|---|
fbWriter | FB_JsonSaxWriter |
sKey | STRING |
sDatatype | STRING |
sProperties | STRING |
Outputs
Name | Type |
---|---|
hrErrorCode | HRESULT |
The PLC attributes can be specified in the following form on the structure elements:
{attribute 'Unit' := 'm/s'}
{attribute 'DisplayName' := 'Speed'}
Sensor1 : REAL;
A complete sample of how to use this method can be found in section Tc3JsonXmlSampleJsonDataType.
Sample call:
fbJsonSaxWriter.ResetDocument()
fbJsonDataType.AddJsonKeyPropertiesFromSymbol(fbJsonSaxWriter, 'MetaData','ST_Values','Unit|DisplayName');